The number of patient visits in emergency rooms nationwide rose from about 95 million in 1997 to 117 million in 2007 -- an increase of 23%.

Only about half of that increase can be attributed to population growth.

The average wait time in ERs rose from 22 minutes to 33 minutes over that period.

Meanwhile, as demand was growing, the number of ERs dropped 5% from 4,114 in 1997 to 3,925 in 2007.

In 1997, about 43% of emergency rooms were considered "safety net" ERs (because roughly one-third or more of their patients were on Medicaid or uninsured). By 2007, the proportion had risen to 63%.

The researchers found that most of the increased demand for emergency room services came from adults covered by Medicaid, the government insurance program for the poor. In 1999, there were 693.9 ER visits per 1,000 Medicaid enrollees; by 2007, that number had ballooned to 947.2 visits per 1,000 enrollees. In part, that's because 4.8 million adults were added to the Medicaid rolls during that time -- an increase of 35%.

During the same 8-year period, the number of children covered by Medicaid jumped 42% thanks to the introduction of the State Children's Health Insurance Program (better known as SCHIP, and now known simply as CHIP). Although SCHIP represented the biggest expansion of Medicaid in its 40-year history, those additional 6.2 million children did not clog up ERs, probably because the program was effective in steering kids to primary care doctors, according to the study.

ER visit rates were stable for people with Medicare, private insurance, and even the uninsured, the study found.

"One of the nation's most severe recessions started in 2008, and with record job losses in 2008 and 2009, an estimated additional 5.8 million Americans became uninsured and an estimated 5.4 million enrolled in Medicaid and SCHIP," they wrote. "An additional 16 million individuals are expected to obtain Medicaid coverage through the Patient Protection and Affordable Care Act of 2010." How ERs deal with these patients is "a critical concern," they concluded.

-- Karen Kaplan/Los Angeles Times

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